Horizontal centrifugal casting method

ABSTRACT

A horizontal centrifugal casting machine is described wherein a sectionalized mold for casting a cylindrical structure, e.g., a finned motor frame, is assembled, the structure cast and the mold sections stripped from the cast structure in an entirely automated process. The casting machine includes a plurality of arcuately shaped mold sections mounted upon jaws capable of being secured to pistons of pulling cylinders. With the pistons extended, the mold sections form a substantially cylindrical structure and dual annular rings having a tapered radially inner face are traversed axially along a tapered outer portion of the jaws to fixedly secure the mold sections in position. After disengagement of the pistons, the mold is rotated by a high speed drive motor whereafter a ladle containing molten metal is inserted axially within the mold and the ladle is tilted to pour the molten metal into the mold. The ladle then is withdrawn and a mandrel assembly supporting the ladle, an expandable arbor and a mold coating device is rotated to register the expandable arbor with the mold. The high speed drive motor then is de-energized and the mold stopped at a predetermined angular position using a low speed drive motor. After the expandable arbor is inserted axially within the mold and the arbor expanded to engage the interior of the cast cylindrical structure, the pistons of the pulling cylinders are driven radially inward to engage the outer surface of the jaws and the annular rings are released to permit the pistons to strip the mold from the cast structure. The cast then is removed from the interior of the stripped sections and the open jaws are coated with casting lubricant permitting the casting cycle to be repeated. To obtain optimum quality in casting finned aluminum motor frames, the rate of rotation of the ladle during the pour should vary to effect a more rapid rate of angular displacement at the initiation and termination of pouring metal from the ladle than at the middle of the pour to produce a constant flow of metal from the ladle.

United States Patent Baumann et al.

[ Feb. 18, 1975 HORIZONTAL CENTRIFUGAL CASTING METHOD [75] Inventors: Frederick William Baumann, Scotia;

Bernard Ceasar Kaczkowski, Schenectady George Mowry Rosenberry, Jr,, Elnora, N.Y.; William Russell Smith, Ballston Lake, all of N.Y.

[73] Assignee: General Electric Company Schenectady, N.Y.

[22] Filed: Feb. 26, 1974 [21] Appl. No.: 446,054

Related U.S. Application Data [62] Division of Ser. No. 277,920, Aug. 4, 1972, Pat. No.

[52] U.S. Cl 164/114, 164/131, 164/137 [51] Int. Cl B22d 13/10 [58] Field of Search 164/114, 131, 137, 292, 164/293, 295, 300, 301, 267, 344, 404

[56] References Cited UNITED STATES PATENTS 1,621,380 3/1927 Ruder 164/300 X 3,397,735 8/1968 Taccone 164/295 X 3,457,986 7/1969 Andrews 164/295 X 3,741,278 6/1973 Baumann et a1 164/114 3,741,707 6/1973 Baumann et al.... 164/292 X 3,821,980 7/1974 LaBahn et al. 164/131 X Primary Examiner-Francis S. Husar Assistant Examiner-John E. Roethel Attorney, Agent, or Firm-Vale P. Myles [57] ABSTRACT A horizontal centrifugal casting machine is described wherein a sectionalized mold for casting a cylindrical structure, e.g., a finned motor frame, is assembled, the structure cast and the mold sections stripped from the cast structure in an entirely automated process. The casting machine includes a plurality of arcuately shaped mold sections mounted upon jaws capable of being secured to pistons of pulling cylinders. With the pistons extended, the mold sections form a substantially cylindrical structure and dual annular rings having a tapered radially inner face are traversed axially along a tapered outer portion of the jaws to fixedly secure the mold sections in position. After disengagement of the pistons, the mold is rotated by a high speed drive motor whereafter a ladle containing molten metal is inserted axially within the mold and the ladle is tilted to pour the molten metal into the mold. The ladle then is withdrawn and a mandrel assembly supporting the ladle, an expandable arbor and a mold coating device is rotated to register the expandable arbor with the mold. The high speed drive motor then is de-energized and the mold stopped at a predetermined angular position using a low speed drive motor. After the expandable arbor is inserted axially within the mold and the arbor expanded to engage the inte rior of the cast cylindrical structure, the pistons of the pulling cylinders are driven radially inward to engage the outer surface of the jaws and the annular rings are released to permit the pistons to strip the mold from the cast structure. The cast then is removed from the interior of the stripped sections and the open jaws are coated with casting lubricant permitting the casting cycle to be repeated. To obtain optimum quality in casting finned aluminum motor frames, the rate of rotation of the ladle during the pour should vary to effect a more rapid rate of angular displacement at the initiation and termination of pouring metal from the ladle than at the middle of the pour to produce a constant flow of metal from the ladle.

3 Claims, 24 Drawing Figures LflLL LADLE WITH REQUIRED QUANTITY OF MOLTEN METAL j I RIVE MOLD SECTIONS INTO CYLINDRICAL CONFIGURATION I DRAW LOCK RINGS AXIALLY INWARI) TO LOCK SECTIONS IN POSITION [BISENGAGE AND WITHDRAW PULLING PISTONS FROM MOLD SECTIONS I I ROTATE MOLD AND CIRCULATE COOLANT INTO MOLD I LINSERT LADLE INTO MOLD AND POUR j STOP MAIN MOLD DRIVE AND INDEX MOLD WITH PULLING PISTONS WITHDRAW more AND ROTATE MAN [i WITH MOLD DREL ASSEMBLY To max THE 1 j INSERT ARBOR WITHIN MOLD AND EXPAND I PULLING PISTONS WITH MOLD SECTIONS AND STRIP FROM REMOVE ensr FROM INTERIOR OF MOLD SECTION A I PRAY HEAD WITH SECTIONS 3 ND INDEX PATENTED FEB l 8|975 SHEET OlUF 15 4 3866561 sum 0uuF15 PATENTEU F531 8 I975 PATENTEU F551 8 I 5 3,866,661 sum use; 15

Hum

HYDRAULIC SOURCE PATH-N W ED F581 8-1975 sum 08 or 15 m wm PATENT Q FEB 1 8 I975 1.8661561 sum lUUF '15 HIIIIIIII llll F'AIENTEUFEB 1 81975 M 1866,6651

SHEET 1 2 0F 15 DRIVE MOLD SECTIONS INTO CYLINDRICAL CONFIGURATION DRAW LOCK RINGS AXIALLY INWARDTO LOCK SECTIONS IN POSITION DISENGAGE AND WITHDRAW PULLING PISTONS FROM MOLD SECTIONS INSERT LADLE INTO MOLD AND POUR STOP MAIN MOLD DRIVE AND INDEX MOLD WITH PULLING PISTONS WITHDRAW LADLE AND ROTATE MANDREL ASSEMBLY TO INDEX THE ARBOR WITH MOLD V INSERT ARBOR WITHIN MOLD AND EXPAND EggfPGE PULLING PISTONS WITH MOLD SECTIONS AND STRIP FROM REMOVE CAST FROM INTERIOR OF MOLD SECTIONS AND INDEX SPRAY HEAD WITH SECTIONS SPRAY STRIPPED MOLD SECTIONS WHILE DRIVING SPRAY HEAD THEREIN RETRACT SPRAY HEAD AND INDEX LADLE WITH MOLD HORIZONTAL CENTRIFUGAL CASTING METHOD This is a division of application Ser. No. 277,920, filed Aug. 4, 1972, now U.S. Pat. No. 3,825,057.

This invention relates to a horizontal centrifugal casting machine for casting finned cylindrical structures and in particular, to a casting machine wherein a sectionalized mold is assembled into a cylindrical configuration, the structure is centrifugally cast within the mold and the mold stripped from the structure in a substantially automated process.

In the manufacture of dynamoelectric machines, a number of diverse techniques heretofore have been proposed and/or utilized to fabricate machine frames dependent upon such diverse factors as the size and number of frames to be cast. For example, high pressured die casting techniques have been employed to produce cylindrical frames below approximately inches in diameter on a high volume basis while maachine frames above 10 inches in diameter generally have been formed commercially by sand casting or extrusion techniques.

While centrifugal casting has been known for many years, centrifugal casting machines primarily have been limited to casting structures having a smooth outer surface, such as metal pipes, or for applying interior linings to preformed objects, e.g., casting brake linings along the interior of brake drums. For example, a centrifugal casting machine is described in U.S. Pat. No. 1,917,872 for casting brake drum linings by inserting a ladle into a metal drum retained in position within a plurality of arcuately shaped segments and gradually tilting the ladle to pour metal at a uniform rate into the drum. Because the mold is separate from the centrifugal casting machine and forms a part of the finished product, there is no need to strip the mold from the centrifugally cast metal. A highly automated centrifugal casting machine for producing smooth surfaced pipes also is shown in U.S. Pat. No. 3,457,986 wherein a plurality of molds are mounted along the periphery of a rotatable turret and the turret is revolved to register the individual molds with circularly disposed stations, i.e., a centrifugal casting station, a spray cooling station, a pipe withdrawal station, etc., to effect the sequential steps of the casting process. Such machine, however, is specifically designed for smooth surfaced objects and would not be suitable for casting finned structures because of the use of expandable tongs to withdraw the cast pipe from the mold.

It also has been proposed (i.e., in Baumann et al U.S. Patent applications, Ser. No. 220,285 entitled Horizontal Centrifugal Casting Machine and Ser. No. 220,286 entitled A Dismemberable Mold For Centrifugally Casting Finned Structures, both filed Jan. 24, 1972), that a sectionalized mold be seated upon horizontal rollers of a centrifugal casting machine to permit substantially automated casting of finned cylindrical structures. Because the mold is not fixedly secured to the casting machine, the mold can be lifted from the rollers by a crane and transported to a stripping machine (such as is described in LaBahn et al U.S. Patent application, Ser. No. 220,280, entitled Method and Apparatus For Automatically Stripping A Sectional: ized Mold From A Cast and Baumann et al U.S. Pa-

2v both filed Jan. 24, 1972) to strip the sectionalized mold from the underlying centrifugally cast structure. While the centrifugal casting equipment and casting methods disclosed in the foregoing applications are highly suitable for casting large diameter finned cylindrical structures, the production rate is somewhat limited by the necessity for transferring the mold from the casting ma chine to the stripping machine. Moreover, because the crane required to transfer the mold from the casting machine to the stripping machine normally is under the control of an operator and because the heat of the mold makes manual assistance in the transfer difficult, substantial labor is required to complete the process notwithstanding the automated nature of each individual machine utilized for casting.

It is therefore an object of this invention to provide a highly automated centrifugal casting machine wherein the mold is assembled, the structure cast and the mold stripped from the cast in a single machine.

It is also an object of this invention to provide a centrifugal casting machine capable of producing a large quantity of cast finned structures on a substantially automated basis.

It is a further object of this invention to provide a centrifugal casting machine having a mold locking assembly capable of securely fastening the individual mold sections into a composite unit for casting while permitting ready disengagement from the mold for stripping the mold sections from the cast structure.

It is a further object of this invention to provide an automated method of casting finned cylindrical structures and stripping the mold from the cast structures.

A horizontal centrifugal casting machine for casting cylindrical structures in accordance with this invention generally includes a plurality of arcuate mold sections having interlocking edges and means connected to the mold sections for moving the sections into juxtaposition to form a cylindrical mold capable of confining the liquid material to be cast. Means also are provided for connecting a rotary drive to the cylindrical mold for rotation of the mold at a predetermined speed and suitable means within the machine pour molten material into the mold during rotation to cast the cylindrical structure. After solidification of the cast structure, suitable means strip the individual mold segments from the cast structure to produce a cylindrical structure indetent application, Ser. No. 220,279 entitled Automated Method Of Manufacturing Finned Machine Frames,"

pendent of the mold into which the molten material was poured. To assure complete stripping of all mold sections from the cast and to prevent fracturing of the cast structure during stripping, the casting machine preferably also includes means for inserting'an arbor within the cast cylindrical structure and means for expanding at least a portion of the arbor in a radial direction to contact the interior of the: cast structure prior to stripping the mold sections from the cast. When the molten material is poured into the rotating mold from a ladle, suitable means desirably are included within the machine to tilt the ladle at a variable rate during the pour, i.e., a more rapid angular displacement of the ladle is desirable at the beginning and end of the pour than at the middle of the pour, in order to produce con stant flow of metal from the ladle and high quality in the finished cast product.

Although this invention is described particularity in the appended claims, a more complete understanding of the invention may be obtained from the following detailed description of a specific centrifugal casting machine formed in accordance with this invention when taken in conjunction with the appended drawings wherein:

FIG. 1 is an elevation of a centrifugal casting machine in accordance with this invention,

FIG. 2 is a plan view of the mandrel'assembly utilized in the stripping machine of FIG. 1,

FIG. 3 is a view of the apertured plate utilized in the speed sensing and mold positioning assembly,

FIG. 4 is an enlarged sectional view of the speed sensing and mold positioning assembly,

FIG. 5 is a sectional view taken along lines 5-5 of FIG. 1 to illustrate the T-shaped groove wherein the gripping jaws slide,

FIG. 6 is an enlarged view of the lock rings utilized to secure the mold in position for casting,

FIG. 7 is an isometric view of the mold in a machine mounted assembly,

FIG. 8 is a view depicting the serial connection of the coolant hoses to the mold sections,

FIG. 9 is a sectional view of the mold pulling assembly,

FIG. 10 is a sectional view of the ladle rotation mechanism,

FIG.,1 1 is a view of the variable pour rate control of the ladle rotation mechanism,

FIG. 12 is a graph illustrating the variation of rate of angular displacement of the ladle with the quantity of aluminum poured from the ladle,

FIG. 13 is a sectional view of the expandable arbor,

FIG. 14 is a view of the arbor taken along lines 14-14 of FIG. 13,

FIG. 15 is a sectional view of the lubricant spray mechanism of the casting machine,

FIG. 16 is an elevation view of the main turntable,

FIG. 17 isa plan view of the main turntable to illustrate the speed control and positioning mechanism of the turntable,

FIG. 18 is a view of the main turntable rotary drive,

FIG. 19 is a sectional view of the mechanical registration piston of the main turntable,

FIG. 20 is a sectional view taken along lines 20-20 of FIG. 17 to illustrate the limit switches controlling FIG. 22 is an electrical diagram of a circuit suitable for controlling the operation of the machine.

A horizontal centrifugal casting machine 10 in accordance with this invention is shown in FIG. I and generally comprises a drive and transmission unit 11, a mold assembly and stripping unit 12 and a mandrel assembly 13. The mandrel assembly (illustrated also in FIG. 2) is rotatable to axially register ladle 14, expandable arbor 15 or lubricant spray head 16 with the mold and the entire mandrel assembly is mounted upon a carriage 17 axially traversable along rails 18 to permit insertion of the registered mandrel component axially into the mold.

DRIVE AND TRANSMISSION UNIT The main drive for horizontal centrifugal casting ma chine 10 is provided by drive motor 19, e.g., a solid rotor motor such as is described in GM. Rosenberry, .lr. US Pat. Ser. No. 3,582,696 speed regulated by the control circuit taught in Rosenberry et al US. Patent Ser. No. 3,582,737 (both of which patents are assigned to the Assignee of the instant invention). Typically the drive motor is operated at a rotary speed of approximately 900 rpm to produce a speed of approximately 500 rpm in rotary face plate 20 to which the arcuate sections of centrifugal mold 21 are secured. Because the drive and transmission unit are subject to multiple starting and stopping during operation, motor 19 desirably is cooled by a blower unit 23 which includes fan 24 driven by motor 25 and suitable ducting 26 communicating the drive motor interior with the external environment.

The drive end 27 of main drive motor 19 rotates a pulley 28 driving flexible belts 29 to apply torque to a larger diameter pulley 30 to obtain the desired reduction in speed between the drive motor and centrifugal mold 21. Because the belt load is too great for direct application to main shaft 31 of the drive and transmission unit, torque transmitted through belt 29 is transferred to the main shaft through a conventional bearing block assembly 32 and standard coupling unit 33. As is shown in FIG. 1, the outer housing 34 of bearing block assembly 32 is fixedly secured to base 35 of the casting machine to support the belt load while a pair of bearings 36 permit rotation of shaft 37 within the bearing block assembly to transmit rotary force through coupling unit 33 to main shaft 31. The torque applied to main shaft 31 through coupling unit 33 then is transmit ted to rotary face plate 20 secured to the hollow main shaft by bolts 38 to permit rotation of centrifugal mold 21 mounted to the face plate (as will be more fully explained hereinafter).

The speed of main shaft 31 is monitored by a speed sensing and mold positioning assembly 39 (illustrated in FIGS. 3 and 4) which includes a selectively apertured wheel 40 mounted upon the shaft to pass between three proximity switches 4l-43 secured to supports 44 mounted to block 45 on base 35. Uppermost proximity switch 41 is radially registered with six arcuately spaced apertures 46 in wheel 40 to measure the rotary speed of shaft 31 by counting the number of actuations of proximity switch 41 within a fixed period of time while lower proximity switch 42 registered with radially outer semicircular lip 47 of wheel 40 is employed to determine whether shaft 31 is rotating by sensing continued actuations of the proximity switch. The third proximity switch 43 serves to position rotary face plate 20 (and mold 21 mounted thereon) at a particular angular orientation with pulling assembly 48 (illustrated in FIG. 1) of the casting machine by aligning the proximity switch with protrusion 49 extending axially outward from wheel 40. Proximity switches, to achieve the foregoing results, are well-known in the art and can be obtained commercially from the General Purpose Control Department of the General Electric Company.

To obtain the desired registration between protrusion 49 and proximity switch 43 (and the resultant registration between centrifugal mold 21 and pulling assembly 48), a small drive motor 50 (illustrated in FIG. 1) is connected to the opposite drive end of the shaft of main drive motor 19 through a gear reducer 51 and an electric clutch 52 to permit slow rotation of main shaft 31 after termination of mold rotation at the end of a cast, as observed by proximity switch 42. Thus, with drive motor 19 stationary after the completion of a centrifugal cast, electrical clutch52 is engaged and small drive motor 50 is energized to" slowly rotate shaft 31 through main drive motor 19 until protrusion 49 is registered with proximity switch 43 at which time energization of the small drive motor is terminated and the motor electric brake is engaged to stop rotation of the mold. Clutch 52 then is disengaged, and the tapered piston of hydraulic cylinder 22 is inserted into a slot in rotary face plate to lock the plate in position.

Main shaft 31 is utilized not only to transmit torque to rotary face plate 20 but also as a conduit to transmit fluid coolant to mold 21 mounted upon the face plate. The fluid coolant, typically water, enters axially outer annular chamber 53 through aperture 54 in water jacket 55 surrounding the end of shaft 31 remote from the mold and the coolant flows through bore 56 in the shaft to a central pipe 57 for axial transmission along the shaft. The fluid coolant then advances into annular chamber 58 formed between partition 59 and plug 60 whereafter the coolant flows radially outward through aperture 61 in the shaft and flexible hoses 62 to pass serially through the four individual sections forming mold 21 (as will be more fully explained hereinafter with reference to FIG. 8). The coolant then returns through aperture 63 to axial flow channel 64 between shaft 31 and pipe 57 to return to annular chamber 65 by way of radial bore 66 in shaft 31. From annular chamber 65, the coolant flows through aperture 67 within water jacket 55 to return to a heat exchange and pumping unit (not shown) for recirculation through the mold. A partition 68 serves to separate the streams of circulating coolant in the adjacent annular chambers at the end of shaft 31 while conventional face seals 69 inhibit leakage of coolant adjacent the shaft.

Main shaft 31 is supported at the driven end of the shaft by a spherical bearing 70 while a tapered roller bearing 71 is situated at the drive end of the shaft to ab-' sorb both radially and axially directed shaft loads. -In conventional fashion, tapered roller bearing 71 is positioned between shaft 31 and housing assembly 72 at a fixed axial location while spherical bearing 70 is axially slidable between the shaft and housing assembly to inhibit axial loading of the bearing. Both bearings are lubricated by oil circulating between the rotating shaft and the stationary housing assembly by way of oil intake and exhaust orifices 73 and 74, respectively,

within the housing assembly.

MOLD ASSEMBLY AND STRIPPING UNIT A pair of hydraulic cylinders 75 mounted on plate 76 fixedly secured to base 35 serve to reciprocally drive mold locking unit 77 in an axial direction thereby securing mold 21 in position for casting. To effect locking of the mold, pistons 78 within cylinders 75 reciprocally drive annular plate 79 and the reciprocal motion of the plate is transmitted through the radially outer raceway of tapered roller bearing 80 to axially traverse the rotary bearing members and the inner raceway of the bearing along shaft 31. Because the inner raceway of bearing 80 also forms an integral part of back plate 81, the back plate and rods 82 fixedly secured along the periphery of the back plate also are traversed in an axial direction by actuation of pistons 78. Axial movement of rods 82 draws the tapered annular face 83 of lock rings 84 against the tapered radially outer faces 85 of mold gripping jaw 86 to radially slide the jaws within a T-shaped aperture 87 (shown in FIG. 5) of rotary face plate 20 thereby locking the four mold sections secured to the respective ones of orthogonally disposed jaws 86 into a composite cylindrical unit. Limit switches 88 are mounted upon the exterior of housing assembly 72 to measure the outward extent of pistons 78, Le, by actuation of the limit switches by vanes: 89 carried upon rod 90 mounted on plate 79.

Because the axially outer and inner lock rings, identified by reference numerals 84a and 8412, respectively, of the mold locking unit may not contact tapered faces 85a and 85b of mold gripping jaws 86 with equal force due to unequal thermal expansion of the jaws during casting, axially outer lock ring 84a is driven by an individual spring biasing means, such as the Bellville washers 92, shown in FIG. 6, to compensate for the effects of thermal expansion. Thus, although rods 82 produce an equal axial advancement of tapered lock rings 84a and 84b upon actuation of hydraulic cylinder 75, thermal expansion of gripping jaw 86 may producea higher clamping force between one ring, i.e., inner ring 84b, and tapered face 85b of the gripping jaw then occurs between outer ring 84a and the gripping jaw. By dimensioning the inner radius of ring 840 to engage the gripping jaw before ring 84b, Bellville washer 92 situated adjacent ring 84a on rod 82 can absorb the axial load as axially inner ring 84 b is driven into firm contact with the associated tapered face on gripping jaw 86 to equalize the force distribution at axially opposite ends of the assembled mold.

A sectionalized centrifugal mold 21 preferred for utilization in this invention is depicted in FIG. 7 in a machine mounted configuration, i.e., with associated gripping jaws 86 of the casting machine. The mold preferably is formed of four arcuate sections 21a21d having interlocking axial edges 93 to mate upon juxtaposition of the sections thereby forming a composite mold capable of retaining molten metal therein. The interlocking edges 93 of mold 21 are similar to the edge configuration of the mold disclosed in Baumann et al US. Patent application, Ser. No. 220,286 (the disclosure of which is incorporated herein by reference). The edges of mold 21, however, are designed to be disengaged or engaged upon simultaneously moving all four sections along perpendicularly oriented axes. To obtain the ready dismemberment of the mold while inhibiting leakage of molten metal from the mold, two diametrically opposite mold sections, i.e., sections 21a and 210, are provided with longitudinal edges having an angular, preferably orthogonal, step 93a which functions as a seat for the longitudinal edges 93b of the adjacent mold sections. The radially inward extending lips 94 at the axial ends adjacent mold sections also have edges 94a with a complimentary angular taper, preferably radial, to snugly mate upon juxtaposition of the mold sections. When the mold is employed to cast frames for dynamoelectric machines, the interior or each mold sections preferably is notched, in conventional fashion, to form a plurality of triangular grooves 91 extending in a substantially parallel direction into each mold section to produce the cooling fins desirable for the cast frame without substantially inhibiting stripping of the mold sections from the frame. To effect such result, the width of the grooves should taper at a suitable anglel, e.g., 0.030/in. n 2.30', with penetration into the sidewall of the mold.

Each mold section is individually secured to a mold gripping jaw of the casting machine by bolts 95 and a suitable fluid connector, preferably a commercially available quick disconnect connector 96 and an elbow 97 (shown in FIG. 8) admits fluid coolant from flexible hoses 62 to the region between the mold section and the jaw fixedly secured thereto. Preferably, the coolant is circulated in dual streams serially through the composite mold jaw units (as shown in FIG. 8) before returning to flow chamber 64 in shaft 31 for return to the heat exchange and coolant pumping unit associated with the machine.

Because lock rings 84 clamp the mold sections into a composite unit, no provision (other than tapered face 85 on the mold gripping jaws) is required along the outer periphery of the mold sections to secure one mold section to the other. Four ears 99, however, (shown in FIG. 7) are provided on each mold section to maintain the sections in juxtaposition in order to facilitate changing molds within the casting machine. Thus, to change the mold for a new frame size, pins 98 can be inserted through the ears of the mold sections to maintain the sections in juxtaposition whereafter the composite unit may be supported upon arbor of mandrel assembly 13. Mandrel assembly carriage 17 then is moved axially into the machine permitting the mold sections to be bolted to gripping jaws 86 of the machine. The pins retaining the mold sections in juxtapositionthen can be manually removed and the arbor withdrawn axially from the mold to permit the initiation of casting.

As was stated earlier, each gripping jaw 86 to which the individual mold sections are secured has a tapered radially outer face 85 at axially opposite ends of the mold to permit the application of a radially inward force to the mold sections upon the axial traversal of lock rings 84 across the faces. One edge of the jaw, the axially inner edge, has a T-shaped protrusion 100 to be slidably received within T-shaped aperture 87 of rotary faace plate to permit the jaw to slide in a radial direction. The radially outer face of each jaw also has a pulling bracket 101 for engagement with pistons 102 (shown in FlG. 1) of hydraulic pulling assemblies 48 fixedly secured to the stationary main back plate 104 of the centrifugal casting machine.

. The pulling assembly utilized to position the mold sections for engagement by lock rings 84 and for stripping the mold sections from the cast is illustrated more clearly in FIG. 9 and generally comprises a large hydraulic pulling cylinder 105, e.g., a 6 inch diameter cylinder, fixedly secured to back plate 104 by brackets 106 and angles 106a. Piston 102 of the pulling cylinder has a tapered bifurcated member 107 threadedly engaged at the forward end ofthe piston to engage pulling brackets 101 along the radially outer face of gripping jaws 86 while an elongated bracket assembly 108 extends outwardly from bifurcated member 107 to support small diameter piston cylinder 109 which drives dual lockpins 110 through aligned apertures 111 in the bifurcated member and the pulling brackets of the jaws upon admission of hydraulic fluid to the small diameter cylinder. Dual limit switches switches 112 and 113 also arae mounted along the outer housing of small diameter cylinder 109 to be engaged by lockpins 110 to indicate the position of the lockpins relative to bifurcated member 107. Similarly, piston 102 of the large pulling cylinder also carries a lower platform 114 having dual guide rods 115 mounted thereon to actuate limit switches 1 16 and 117 by vanes 118 mounted on the guide rods to indicate the extent of piston 102 toward the mold. In order to permit both the positioning of the four arcuate sections of mold 21 into a cylindrical structure prior to casting, and the stripping of the mold sections simultaneously from the cast, four pulling cylinders 105 are mounted at 90 intervals about main back plate 104 to radially align bifurcated members 107 with pulling brackets 101 of gripping jaws 86.

To assure that the four pulling pistons operate simultaneously during stripping of the mold from the cast. the four pulling cylinders are fed hydraulic fluid through commercially available flow dividers (not shown) to synchronize the pulling of the mold sections from the cast notwithstanding differing adhesive forces between the cast and the separate mold sections. Flow dividers to achieve this result typically include four hydraulic pumps having a single interconnected shaft to assure the pumping of equal quantities of hydraulic fluid to each of pulling cylinders 105. Thus, all the pulling pistons are withdrawn into their respective cylinders at a uniform rate and there is substantially no withdrawal until all mold sections are broken loose from the cast.

Should the slip rate ofthe pumps forming the hydraulic fluid flow divider become excessive, two flow dividers can be connected in series in the hydraulic lines, e.g., a flow divider capable of pumping seven gallons per minute per cylinder could be serially connected with a flow divider capable of pumping gallons per minute per cylinder. The lower volume flow divider then functions to reduce the slip between pulling pistons until the mold sections are disengaged from the cast whereafter a suitable valve by-passing the lower volume flow divider could be actuated to permit a more rapid synchronized withdrawal of the pulling pistons into their respective cylinders under the control of the higher volume flow divider.

MANDREL ASSEMBLY As was heretofore mentioned with respect to FIG. 2, mandrel assembly 13 is formed of a ladle 14, an expandable arbor 15 and a lubricant spray head 16 protruding outwardly from an upwardly extending centerpost 120 at angulary displaced locations, shown at 90 intervals, to permit axial registration of each of the outwardly extending components with the assembled mold upon rotation of the centerpost. Ladle 14 is substantially identical to the ladle described in heretofore cited Baumannet al US. Patent application Ser. No. 220,285 (the disclosure of which is incorporated herein) and generally includes a cylindrical vessel 121 having a ceramic lining 122 and a metallic outer sheathing 123. In conventional fashion, a rectangular opening 124 is provided along the top of the ladle to admit and remove molten metal from the ladle and the ladle is secured to a rotatable shaft 125 to permit tilting of the ladle when discharge of molten metal from the ladle is desired. A back plate 126 also is mounted between the ladle and rotatable shaft 125 to mate with opening 127 in hood assembly 128 to entirely enclose the rotating mold during the pouring of molten metal into the mold.

Tilting of the ladle to pour molten metal therefrom is accomplished utilizing ladle rotating mechanism 129 (illustrated in FIG. 10 and 11) which mechanism generally includes a hydraulic cylinder 130 fixedly secured within the mandrel assembly for driving rack 131 meshed with gear 132 fixedly mounted upon rotatable shaft 125 of the ladle. The hydraulic cylinder itself is actuated by a hydraulic pressure source 133 through a 

1. A method of centrifugally casting finned cylindrical structures comprising juxtaposing a plurality of arcuate sections to form a horizontally disposed cylindrical mold, rotating said mold at a predetermined speed, pouring molten material into said mold to centrifugally cast said finned cylindrical structure, registering said cast structure with a horizontally disposed arbor, obtaining relative movement between said arbor and said cylindrical structure to insert said arbor within said structure, expanding at least a portion of said arbor into contact with the interior surface of said cast structure, applying a radially outward force to each said arcuate section to strip said section from said cast cylindrical structure, removing said cast structure from the interior of said stripped mold sections and applying a radially inward force to said sections to reassemble said horizontally disposed cylindrical mold for casting a subsequent structure.
 2. A method of centrifugally casting finned cylindrical structures according to claim 1 wherein pouring of said molten material into said mold is accomplished by pouring a quantity of molten material proportional to the size of the cylindrical structure to be cast into a ladle, inserting said ladle axially into said mold, tilting said ladle to pour said molten material into said mold, axially removing said ladle from said mold and further including rotating said ladle and said expandable arbor upon a common mandrel to axially register said arbor with the cast cylindrical structure prior to insertion of said arbor in said structure.
 3. A method of forming cylindrical cast objects comprising juxtaposing a plurality of mold sections to produce a cylindrical mold, centrifugally casting a cylindrical structure within said juxtaposed mold sections by inserting a ladle within the mold and tilting the ladle to pour molten material from said ladle to said mold, axially removing said ladle from said mold, registering said mold with a horizontally extending arbor, inserting said arbor within said mold, extending at least a portion of said arbor to engage the interior of said cast structure, stripping said mold sections from said cast structure to insulate a structure formed entirely of molten material, removing the cylindrical structure from the interior of said stripped mold sections, spraying the interior surface of said stripped sections while in an open position, and subsequently moving said mold sections radially inward to form a cylindrical mold for subsequent casting. 